Backport casting fix for MSVC compilation from zyre
Backport casting fix for MSVC compilation from zyre

hintjens/zproto,bkmit/zproto,sappo/zproto,sphaero/zproto,hintjens/zproto,hintjens/zproto,hintjens/zproto,c-rack/zproto,jemc/zproto,zeromq/zproto,c-rack/zproto,jdiez17/zproto,c-rack/zproto,sphaero/zproto,somdoron/zproto,zeromq/zproto,vyskocilm/zproto,sappo/zproto,jdiez17/zproto,sphaero/zproto,jdiez17/zproto,bkmit/zproto,jdiez17/zproto,asokoloski/zproto,vyskocilm/zproto,c-rack/zproto,c-rack/zproto,sphaero/zproto,somdoron/zproto,zeromq/zproto,somdoron/zproto,sappo/zproto,bkmit/zproto,asokoloski/zproto,jemc/zproto,sappo/zproto,jemc/zproto,asokoloski/zproto,zeromq/zproto,jemc/zproto,jemc/zproto,sappo/zproto,hintjens/zproto,jdiez17/zproto,asokoloski/zproto,jdiez17/zproto,sphaero/zproto,bkmit/zproto,asokoloski/zproto,c-rack/zproto,vyskocilm/zproto,zeromq/zproto,somdoron/zproto,sphaero/zproto,vyskocilm/zproto,somdoron/zproto,sappo/zproto,c-rack/zproto,bkmit/zproto,bkmit/zproto,vyskocilm/zproto,somdoron/zproto,hintjens/zproto,hintjens/zproto,vyskocilm/zproto,vyskocilm/zproto,bkmit/zproto,jdiez17/zproto,zeromq/zproto,asokoloski/zproto,jemc/zproto,sappo/zproto,asokoloski/zproto,jemc/zproto,somdoron/zproto,zeromq/zproto